Surface heater for electric ranges



June 1, 1948. F. H. M CORMICK SURFACE HEATER FOR ELECTRIC RANGES OriginlFiled July 5, 1940 '4 Sheets-Sheet l June 1, 1948.

F. H. M CORMICK SURFACE HEATER FOR ELECTRIC RANGES 4 Sheets-Sheet 2Original Filed July 5, 1940 88 86 ea 92 /05 K22 June 1, 1948. MCCORMICK2,442,659

SURFACE HEATER FOR ELECTRIC RANGES Original Filed July 5, 1940 4Sheets-Sheet 3 HHHLHH HHHH INVENTOR.

qhAglk e-w June 1, 1948. F. H. M CORMICK SURFACE HEATER FOR ELECTRICRANGES 4 Sheets-Sheet 4 Original Filed July 5, 1940 F iy 9.

Patented June 1, 1948 UNITED STATES PATENT OFFICE SURFACE HEATER FORELECTRIC RANGES Francis H. McCormick, Oakwood, Ohio, assignor to GeneralMotors Corporation, Dayton, Ohio, a corporation of Delaware Originalapplication July 5, 1940, Serial No. 344,018, now Patent No. 2,320,041,dated May 7 25, 1943. Divided and this application March 19, 1943,Serial No. 479,689

Claims. 7 V 1 This invention relates to a domestic appliance and moreparticularly to surface heaters for electric ranges.

This application is a division of my copending application Serial No.344,018, filed July 5, 1940, forDomestic appliance (Patent 2,320,041,granted May 25,1943) 7 It is an object of -m invention to provide asurface heater of the tubular sheath type in which the upper surface ofthe sheath is held rigidly in a single plane.

It is another objectof my invention to provide an arrangement for asurface heater of the tubular sheath typewhereby the heater can bereadily cleaned without disturbing the electrical connections.

It is another object of my invention to provide an arrangement of asurface heater of the tubular sheath type in which the terminalconnections are adequately shielded from spillage.

It is another object of my invention'to provide aterminal member for asurface heater in which theterminal connections are so located as to beprotected from spillage.

It is still another object of my invention to provide a surface heaterof the tubular sheath type in which the sheath is very small in diameterso that it may bemore readily formed into the desiredrconfiguration inorder to obtain the desired heat distribution.

It is another object of my invention to provide a two-element surfaceheater of the tubular sheath type having an improved configuration toprovide improved heat distribution.

Furtherobjects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanylngdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. 1 is atop view of one of the surface heaters of anelectric rangeincluding its terminal block;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1; r

Fig. 3 is a sectional view taken along the line 3-4 of Fig. 1;

Fig. 4 is a sectional view taken along the line ll of Fig. 3;

"Fig. 5 is a sectional view showing the method of lifting up one of thesurface heaters for cleaning purposes;

Fig. .6 is an exposed view of the terminal block and connections;

Fig. '7 is a sectional view-of the terminal block taken along-the linel-1 ofFig. 2;

Fig. 8 is a sectional view taken along the line 8-8 of Fig. 2; I

Fig; 9 is a top view of a larger heating unit; and Y.

Fig. 10 illustrates the method of welding used to construct the unit.

As shown in Fig. 5, my improved heating units are provided withextensions connecting with the terminal block so shaped that the surfaceheating units may be readily tilted up for cleaning purposes withoutdisturbing the electrical connections. The terminal blocks are so formedthat the connectionsfrom the surface heating units and from the switchmechanism enter upon the bottom sides of the block so that the entrancesare protected from spillage from above as shown in Fig. 2.

I have shown an electric range in which the surface heaters are of thetubular sheath type. The surface'heaters' are of the two-element typefor general operation with a three-Wire Edison circuit with the innerelement operating at maximum wattage when connected to a volt circuitand the outer element operating at maximum Wattage when connected to a230 volt circuit. The two'elements of each unit are welded to aframework and surrounded by a ring in order to insure rigidity. The endsof each of the connections extend downwardly and thence are curvedoutwardly to terminate in their respective terminal blocks which arelocated beneath thetop surface of the electric range where they areshielded from spillage.

Referring now to the drawings and more particularly to Fig. 1 there isshown a surface heating unit 26 supported in the flanged aperture of thesupporting top 22 of an electric range. This heating unit includes aninner element 6i? and an outer element 62.

The inner element 60 begins with a looped end 64 and extends in aclockwise direction around a central disk 66 to the extent of nearly 360after which it extends radially outwardly as indicated by the referencecharacter 68, thence downwardly to form a portion indicated by thereference character 10 followedby a lower portion 12 which is curvedoutwardly and upwardly so that its two ends enter the termina1 block 14upon its 'face 16. This face 16 is turned slightly downwardly sothatliquid cannot drain into the interior of the'termin'al block throughthe apertures provided for the sheathed elements. The outer element 62begins with the looped end l8 which is adjacent the radially extendingportion 68 and extends in a counter-clockwise direction around the innerelement 60 until it again reaches the radially extendingportion 68,after which it extends directly downwardly as designated by thereference character 80,,fol1owed by an outer upwardly extending curve 82so that it also enters the terminal block 14 through the face 75. Thedownwardly and outwardly extending portions of both elements are allparallel.

Eachof theelements contains. a-helical electrical conductor such as theconductorst and 86. These conductors are each surrounded'by amagnesiumoxide designated by the reference character 88, and the insulatingmaterial is enr closed Within a tubular metal sheath, preferably of highchrome-nickel steel. The sheath of the inner element is designated bythe reference character 90 and the sheath of the outer element by 92.The elements may be madeby any suitable process, for example, onesimilar to that shown in the Lightfoot Patent 1,3593% may be used forits manufacture. After the elements are bent to the shape shown in Fig.1 they are slightly flattened upon their upper surface as shown in Figs.1 and 2, thus providing a greater contact area with the kitchen utensilsused.

These elements are rigidly supported upon a frame-work formed by thecrossed stainless steel channel members 94 and 96 which are eachprovided with a narrow bead 95 for contact welding the members to thebottoms-of the elements as hereafter explained. These channels arenotched at their centers to provide an overlapping joint beneath theornamental disk 66 whichis fastened to another disk 98 which in turn isspot-welded to the channel members 94 and 95 in order to reinforce theiroverlapping joint to firmly hold the channel members together.

The elements 60 and 62 are preferably fastened to the crossed channels94 and 96 by contact or projection welding. This step is illustrated inFig. 10 whichshows a portion of the inner element 60 together with" aportion of one of the channels 95. As shown, the crossed channel membersare supported upon a lower supporting member I52 which is shaped so thatit supports the channel members directly beneath the narrow'bead 95which is provided for welding purposes. The two elements are then placedupon the crossed channel members in proper position after which apivoted weighted member 154 is brought to bear upon the upper surface ofthe elements 60 and 62 in order to hold them 'firmly upon the variousportions of the bead 95. The lower supporting member I52 is-connected bya suitable conductor I56 to the secondary coil I58 of a transformer. Theprimary coil I60 of the transformer is connected to apower source'underthe control of a manual switch I62. Theother end of the secondary coilI58 is connected by'a conductor I 64 to a pivoted supporting arm I65 forthe weighted member I54. When the switch I 62 is closed currentpasses'through the secondary circuit and sufficient current to Weldpasses between the elements and the channels at the crossing pointsbetween the beads and the various portions of the elements. Thisprovides a simple method for simultaneously welding the elements to thechannels at the crossing points and insures'a substantially flat topsurface for all portions of the elements forming the main portion of theheating unit. I ;call this projection welding.

The opposite endsof the channel members are provided with notchessimilar to the notch IIlI in Fig. 3. Each of these notches Illl receivesthe adjacent struck-in portion I03 of the rim I05 whichsurrounds-theouter element 62. The ends of the channels are each provided withadownwardly projecting lip IIlI which together with a lower projection[09 firmly locks the ends 'ofthe channels to the projecting portions ofthe rim I05. The lower projections :III9 are bent .outwardly as shown indotted lines in Fig. 9 in order to allow'the projection I513 tobe placedin the notch IfiI. After this'the projections H39 are bent straightagain so that the projections I03 are firmly locked in place withinnotches IIII.

' The rim Iiifiis made from a straight strip of metal and is curled intocircular form with its joint adjacent the terminal I4. This joint ismade rigid by the connecting piece III which is welded to the two endsof the strip forming the rim so as to make a firm joint which ispractically invisible. This connecting piece III also serves to locatethe surface heaters radially,

since it is provided with a tongue adapted to register'with the notch II3 provided in the flange H5 surrounding the aperture provided in thesupporting surface 22 of the range. The rim IIl5 is provided with aflange II! which rests upon the flange II5 of the supporting top 22..By'this construction the upper surfaces of each element are'maintainedrigidly in a single plane.

Beneath each heating unit is a metal reflector I9 which may be formed ofaluminum coated steel, chrome plated metal or stainless steel in orderto reflect the radiant energy from the heating elements for insulatingpurposes. This reflector II9 reflects any heat rays from the heatingelement upwardly onto the bottomsurface of the container being used uponthesurface heater. The reflector H9 is provided with the flange IZIwhich rests upon the flange 5 beneath the rim I95. The reflector H9 is.provided with the drain aperture I23 beneath the central disk 66 so asto catch and drain any spillage which may fall between the convolutionsof the heating elements from the containers used on top of the range.The'spillage will-pass through the flanged aperture I23 onto a drain pannormally provided beneath the reflector. The reflector H9 is providedwith a cut-outor cut-away portion I25 through whichthe downwardlyextending portions I0 and 8B of the inner and outer heating elementspass. 7

It should be notedthat the terminal block"'I-"-,is not beneaththeheating unit but is beneath the supporting top 22 of the range sothatany liquid which spills upon the heating .unit willnot fall upon theterminal block and, possibly enter to cause'a short circuit. 'Also bycurving theater minal outwardly in the manner describedthe entireassembled heating element may be lifted upwardly as shown in Fig. 5without disturbing the electrical connections to the switch mechanism.This exposes the reflector I I9 which may also be lifted and entirelyremoved for more convenient cleaning if desired, without furtherdisturbance. p

Within the sheathing of each element, the helical electrical resistorsare connectedat their ends to a solid electrical conductor terminal suchas the conductor terminal -I3I. This conductor I3l protrudes from theend of the sheathing which is cut off to expose the end-of the solidconductor terminal I3I. The end ofsthershea'thin is fitted into a metalcap I 33 whic'h'is fastened to the terminal block Mby the screws whichare threaded into the bushing I21. "The terminal block I4 is molded ofsome suitable electrical insulating plastic as shown in fFig. 6

with the threaded bushing I21 lodged directly The threaded aper ture MEin each of the terminal lugs l 31 then registers with the center of oneof the round passages I43 extending to the face I45 of the terminalblock 14. A cup washer l4! fits into each of the recesses I43 and one ofthe binding screws I43 receives the eyeletted end of one of the flexibleconductors I50 extending from the switch mechanism. Each of thesebinding screws extend through the aperture in one of the cup washers M1and is threaded into one of the terminal lugs IS! in order to providethe necessary electrical connection between the particular flexibleconductor extending from the switch mechanism and the conductor terminall3! which connects to the helical conductor within the sheathing. Whenin operating position, the face 16 as well as the face I45 of theterminal block 74 are each turned partially downwardly so that liquidfalling upon the terminal block in its normal position will not enterthe passages provided for the different conductors but these passageswill be protected by the impervious upper faces of the block.

This two-part heating unit is connected to a three-wire Edison circuitthrough a multi-heat switch mechanism to secure various other lowerwattage inputs with resulting changes in heat distribution for variouscooking purposes. Several of the circuits which apply are disclosed inmy copending application S. N. 236,471, filed October 22, 1938 (Patent2,259,258, granted October 14, 1941).

In Fig. 9 I have shown a heating unit which is larger in size than theunit shown in Figs. 1 to 5, but which is identical in other respectsexcepting that the outer element 222 is provided with a loop 220 withinthe inner element 224. Like the smaller unit 26 the larger unit issupported within the flanged aperture of the range top 226 which coversthe terminal block 228. The unit is provided with a rim 236 which restsupon the flange of the aperture in the range top 226. This rim isprovided with struck-in portions 232 which support the ends of thecrossed stainless steel channel members 234 which are each provided witha narrow welding bead 236 upon which rests the bottoms of the twoelements at the points at which they cross the channel members 234. Thechannel members 234 are provided with a central disk 238 as in thesmaller unit. The elements 222 and 224 are fastened to the crossedchannel members by projection welding as in the smaller unit. The endportions of the elements extend downwardly and are curved outwardly sothat they extend into one of the downwardly turned faces of the terminalblock 228 exactly in the manner as shown best in Figs. 2 and 5 inconnection with the smaller unit.

The provision of the additional inner loop 220 of the outer element 222greatly improves the heat distribution of the larger unit by providingheat in the center as well as the edge portions by the outer element andin particular makes it possible to make the outer element much longerthan the inner element. This lends itself admirably to my preferredarrangement of operating the inner element at a. maximum wattage upon115 volts and the outer element at maximum wattage upon 230 volts instandard three-wire Edison circuit.

As mentioned in connection with the smaller unit, the elements of thelarger unit are connected by flexible electric conductors to a multiheatswitch mechanism which in turn is connected to a three-wire Edisoncircuit source in order to secure various lower wattage inputs withresulting changes. Several of the circuits which apply are disclosed inmy copending application S. N. 236,471, filed October 22, 1938.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims whichfollow.

What is claimed is as follows:

1. An electric surface heater including a tubular sheath type heatingelement, an inverted channel supporting member transverse to the heatingelement having a bead formation in the longitudinal central portion ofsaid supporting member extending transversely to and in contact with theadjacent tubular portions of the heating element, said heating elementbeing welded to said formation at said points of contact.

2. An electric heater including a circular rim, intersecting invertedchannel members extending transversely across the rim and fastened attheir ends to the rim and secured together at their intersection, and aheating element supported upon and welded to the longitudinal centralportions of said members to form a unitary structure.

3. An electric surface heater including a sheathed heating elementhaving a sinuous form, a plurality of cross supporting inverted channelmembers intersecting said element at a plurality of points along thelongitudinal center lines of said members, said element and membersbeing welded together at said plurality of points.

4. An electric surface heater including a sheathed heating elementhaving a sinuous form, a cross supporting inverted channel memberintersecting said element at a plurality of points along th longitudinalcenter line of said member, said element and member being weldedtogether at said plurality of points.

5. An electric heater including a circular rim, intersecting invertedchannel supporting members extending transversely across said rim andfastened at their ends to the rim and fastened together at theirintersection, a tubular sheath heater element having a sinuous formintersecting said supporting members at a plurality of points along thelongitudinal center of said members, said element and members beingwelded at said plurality of points.

FRANCIS H. MCCORMICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,085,089 Lachman Jan. 20, 19141,998,330 Nicholson et al Apr. 16, 1935 2,094,480 Vogel Sept. 28, 19372,214,583 Hepler Sept. 10, 1940 2,302,808 Smith Nov. 24, 1942' FOREIGNPATENTS Number Country Date 636,652 Germany Oct. 12, 1936

